The present invention relates generally to wireless communication devices and more particularly to a novel radio frequency identification (RFID) tag and to a method of manufacturing said RFID tag.
Current inventory and manufacturing methods rely on the ability to track and identify items, such as packages, containers, individual parts, inventory items or other similar items of concern, and to communicate information relating to said items in a wireless manner. One method of tracking and providing information relating to an item is to incorporate a wireless communication device, such as an active or passive transponder, into an identification tag that responds to wireless interrogation and commands and, in turn, to attach said identification tag directly to the item. The tag is preferably designed to store or represent pertinent information relating to the item to which it is attached, such as a unique identifying number, an expiration date, a “born on” date, manufacturing information, shipment status and the like.
A radio frequency identification (RFID) tag is one well-known type of wireless communication device which transmits and/or receives information relating to an item using radio frequency (RF) signals.
One well-known type of RFID tag includes an antenna and an integrated circuit (IC) chip mounted on the antenna. The aforementioned components are typically enclosed within a two-piece plastic housing or package. In operation, the IC chip is programmed to store pertinent information relating to the item to which the RFID tag is secured. In response to an appropriate interrogation signal, the IC chip converts said programmed information into a corresponding electromagnetic signal which is propagated as radio frequency (RF) waves by the antenna.
Although RFID tags of the type described above are suitable for use on many different types of items, such tags are not well-suited for use on metallic items for the reason that metallic items tend to interfere with the RF signal transmitted by the RFID tag antenna.
Accordingly, one approach to remedy this problem has been to provide the RFID tag with a metallic reflector which makes the RFID tag more tolerant of nearby metals while retaining its RF functionality. Specifically, a metallic reflector is secured to the outer surface of the plastic package housing the antenna and IC chip. In use, the metallic reflector functions as an electrically conductive back plane which reflects RF signals transmitted by the RFID tag antenna away from the metal item to which the RFID tag is secured. In this respect, the metallic reflector serves to effectively insulate the RFID tag from the metal object to which it is secured, which is highly desirable.
An example of an RFID tag of the aforementioned type is disclosed in U.S. Pat. No. 6,501,435, inventors King et al., which issued Dec. 31, 2002, and which is incorporated herein by reference.
RFID tags having a metallic reflector are commonly manufactured in the following manner. First, using injection molding, a plastic base and a plastic cover for the RFID tag package are separately formed, the base and/or the cover being appropriately contoured to matingly receive the RFID tag package. After said injection molding step, the RFID tag antenna, which is commonly constructed as a thin strip of etched copper foil, is secured to the top surface of the plastic base. It should be noted that, rather than securing the antenna to the base in a separate step, the plastic base may, in the alternative, be injection molded around the antenna. Either immediately prior to or immediate after the antenna is secured to the base, the IC chip for the RFID tag is soldered to the top surface of the antenna. With the antenna and IC chip coupled to the base, the plastic cover is then sonic-welded, by hand, to the top of the plastic base so as to enclose the antenna and IC chip therebetween. In a final step, the metallic reflector is secured to the bottom surface of the base using an adhesive.
RFID tags manufactured in the method described above suffer from a couple of notable shortcomings.
One such shortcoming of the foregoing approach is that the molds used to make the injection molded base and cover are typically only sized for use with an antenna (and IC chip) of a particular size. Consequently, if one wishes to vary the dimensions of the antenna (e.g., to tune the antenna for different applications), one must obtain new molds for manufacturing the base and cover. This is highly undesirable as molds are quite expensive.
Another shortcoming of the foregoing approach is the low throughput of the process for manufacturing and assembling the tag. As noted above, each tag is manufactured, one at a time, using a labor-intensive and time-consuming process.